The social determinants and ecological consequences of indiscriminate hunting in tropical Asia

Abstract

Overexploitation is one of the most prominent threats facing IUCN Red-­Listed mammals and birds, particularly in the tropics. Classical bio­economic models focused on single species have proposed techniques for managing exploited populations. Unfortunately, such models and policy instruments based on these principles have failed to prevent population collapse. I posit that this is due to the fact that hunting exploits multiple prey species simultaneously, particularly in open-­access systems typical of the developing world. Moreover, the assumption that hunting is driven by economic or subsistence aims alone may be inaccurate.

Using illegal hunting of mammals and birds Southwest China as a case study, I found that hunting activity was largely sustained by resilient ungulate and passerine stocks. As hunting effort has persisted, more sensitive species have been driven locally extinct. Recreation was the main motivator of hunting, which may be widespread in the developing world but heretofore under-appreciated. Recreational hunters may be less likely to reduce effort when prey populations and catch decline, increasing the likelihood of hunting-mediated extirpations.

Monitoring trends in hunting effort largely depends on human subjects interviews, and indirect surveys are powerful tools when hunting is criminalized. However, analyzing indirect survey data has been challenging: practitioners often lack the means to analyze their findings in a scientifically sound manner. I have developed an open-source software package that permits for several novel analyses and can control for evasive responses. I then applied these techniques to determine what factors are associated with illegal hunting in Southwest China.

I explored what rules may structure hunter prey choice decisions, in order to understand how salient traits could simplify otherwise complex indiscriminate harvesting systems. In many hunting systems, the most relevant trait is body mass. I then incorporated the predicted lower bound on body mass into a theoretical model that combines indiscriminate harvesting with allometric scaling for population growth rates. This model explores the conditions under which large-bodied mammals and birds can be harvested to extinction.